Electromagnetic shielding of a magnetic resonance (MR) imaging system is an important requirement for reliable operation thereof and a basis for generation of high quality diagnostic images. Such an electromagnetic shielding is provided as a Faraday cage to enable a shielding of RF irradiation. Accordingly, components of the MR imaging system involved in the generation or measurement of electromagnetic fields as well as components for analogous signal transmission require a shielding. In particular, the main magnet with gradient and RF coils, which surround an examination space, are located within a shielding, which is typically provided as an exam room shielding.
Electromagnetic shielding becomes more complicated when an MR imaging system is used together with at least one other device, which has to be located in vicinity of the MR imaging system. This refers to a combination of the MR imaging system with other diagnostic or treatment devices, for example the combination of a linear accelerator (linac) device with an MR imaging system. Such a combination enables e.g. the generation of diagnostic images with the MR imaging system during the treatment with the linac device for controlling the operation of the linac device and the efficiency of the treatment using the linac device.
The U.S. Pat. No. 4,613,820 discloses a radio-frequency shielded room for a nuclear magnetic resonance imaging system. An electrically conductive shield wall enclosing a volume is provided adjacent to one end of the magnet bore.
For the MR imaging system, the linac device is an important source of electromagnetic interferences and vice versa, since both devices generate RF irradiation during operation. Another example for such a diagnostic or treatment device is a hyperpolarisation device. Accordingly, it is required to adapt the electromagnetic shielding of the MR imaging system to achieve a reliable RF-shielding thereof under consideration of spatial requirements as well as structural requirements for locating and supporting the other device as well as the MR imaging system. In particular, a reliable shielding of the MR imaging system from electromagnetic interferences generated by the other device is required. Furthermore, also the other device may require shielding from the electromagnetic irradiation generated by the MR imaging system.
An improved electromagnetic shielding comprises a tubular shielding device, which is arranged to surround an examination tube of the magnetic resonance imaging system. Usually, also gradient coils of the MR imaging system, e.g. as a gradient coil assembly, are positioned within the tubular shielding device. The shielding extends from the longitudinal ends of the tubular shielding device to enable access for staff and patients. This results in the exam room shielding being separated by the tubular shielding device into two spaces, one at each longitudinal end of the tubular shielding device. Accordingly, access to the examination tube is rather complicated, especially when access to the examination tube is required alternately from the opposite ends thereof. The access refers to access for maintenance purposes as well as during normal operation. For example, a patient can be placed into the examination tube from one of its ends, and the provisioning of additional coils or supplementary devices like contrast agent supply devices or oxygen supply devices may require access from the opposite end of the examination tube. This is rather uncomfortable for patients and staff.
Additional aspects when using MR imaging systems together with other devices are system installation, maintenance, and repair, which have to be considered in the design of the exam room shielding. The separation of the space by the exam room shielding increases the effort for installation, maintenance, and repair.